A New Measure of Process Capability for Non-Normal Process :  $C_{psk}$

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Journal of Korean Society for Quality Management > Volume 26(1); 1998 > Article

Journal of Korean Society for Quality Management 1998;26(1): 48-.

비정규 공정에 대한 공정능력의 새로운 측도: $C_{psk}$

김홍준¹, 송서일²

¹대구산업전문대학 산업안전과
²동아대학교 산업공학과

A New Measure of Process Capability for Non-Normal Process : $C_{psk}$

ABSTRACT

This paper proposes a fourth generation index $C_{psk}$, constructed from $C_{psk}$, by introducing the factor｜$mu$-T｜ in the numerator as an extra penalty for the departure of the process mean from the preassigned target value T. The motivation behind the introduction of $C_{psk}$ is that when $T eqM$ process shifts away from target are evaluated without respect to direction. All indices that are now in use assume normally distributed data, and any use of the indices on non-normal data results in inaccurate capability measurements. In this paper, a new process capability index $C_{psk}$ is introduced for non-normal process. The Pearson curve and the Johnson curve are selected for capability index calculation and data modeling the normal-based index $C_{psk}$ is used as the model for non-normal process. A significant result of this research find that the ranking of the six indices, $C_{p}$, $C_{pk}$, $C_{pm}$, ${C^*}_{psk}$, $C_{pmk}$, $C_{psk}$in terms of sensitivity to departure of the process median from the target value from the most sensitive one up to the least sensitive are $C_{psk}$, $C_{pmk}$, ${C^*}_{psk}$,$C_{pm}$, $C_{pk}$, $C_{p}$.